Rockers hitting valve covers - Impala Tech
Engine General Engine Discussion.

 
LinkBack Thread Tools
post #1 of 8 (permalink) Old 09-18-2016, 03:30 PM Thread Starter
Member
 
Join Date: Jul 2016
Posts: 74
 
Question Rockers hitting valve covers

It seems like a new mystery every day! Keep in mind I recently bought this car (62 SS) and I didn't build the motor. Had some engine noise that was a concern, stopped by a local shop to get an opinion. Mechanic says he thinks there is one or more rockers hitting he valve cover!! So I take off the valve cover on the noisy side and sure enough there are three definite marks where the rockers were hitting, enough to cause a very small dent!! Discover what I have are 58-64 327 style valve covers on a '69 350. Apparently the 327 style covers have a tapered profile, getting slightly narrower at the top as opposed to straight sides! Obvious solution is to change covers, but my question is what is actually the difference in the heads or rockers that the 65 and up motors require a wider or "non" tapering cover?? Just curious if anyone has run into this before or you can explain what is different about either the rockers or heads. Thanks! Bob
rbwinston is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old 09-18-2016, 03:56 PM
Moderator
 
Join Date: Jan 2006
Posts: 11,059
 
Difference is in the cam. Cam's have been growing in lift and shrinking in lobe separation angle since the sixties. What today is a mild street/strip cam would be classified as a wild race cam back then. In the old days you had a stock cam a three quarter race cam and a full race cam. Today cam profiles will fill a book, and do in terms of cam catalogues.

The early 327 valve covers had an indented bill board in the center of the cover for the placement of the TurboFire decal that called out displacement and rated horsepower before that decal went to the air cleaner (saving GM the cost of one decal to increase profit and pay for the annual Christmas party). Those covers could cause rockers to hit on todays high lift long duration cams, especially with long slot rockers or a roller rocker.

Big Dave
Big Dave is online now  
post #3 of 8 (permalink) Old 09-18-2016, 05:58 PM Thread Starter
Member
 
Join Date: Jul 2016
Posts: 74
 
Red face

Just pulled the other valve cover and exactly the same....three rockers hitting. Going to go to tall style, straight side covers and be done with the problem. Interesting, I also have an oil leak problem that I now suspect could very well be from the valve covers being banged into by the rockers and loosening the seal on the cover gasket!! Wouldn't that be great to find it's not a rear main seal after all!!! Outer edges of the gaskets are quite oily, indicating a good possibility of a valve cover gasket leak. From there it could easily follow down along the block and drip off the back of the motor. Keeping my fingers crossed!!
rbwinston is offline  
 
post #4 of 8 (permalink) Old 09-19-2016, 02:41 PM
BA.
Lifetime Premium Member
 
Join Date: Aug 2008
Location: Miamisburg, Oh.
Posts: 2,779
Blog Entries: 15
 
If I recall correctly, I used to have a similar issue, but I don't think it was as bad as yours sounds to be.

I had a 327 with double-hump heads and had upgraded to a very lopey 292/244 .507 Comp Cam (albeit with Crane Hi-Intensity bleed-down lifters) and my valve covers had a slight tell-tale marks of the aluminum roller rockers hitting them.

Sounds like you got the fix underway, good luck!
BA. is offline  
post #5 of 8 (permalink) Old 09-19-2016, 11:05 PM
Senior Member
 
Join Date: Apr 2013
Location: Canada
Posts: 271
 
I have never seen a hydraulic cam with enough lift (and using a stock stamped steel rocker arm) that had any issues hitting a stock 327 valve cover IF the valve cover is installed the right way. If they are installed the wrong way, yes, they hit.

But, I haven't seen everything either. Maybe it is simply too much lift but I am guessing your covers may be on wrong.
Darth is offline  
post #6 of 8 (permalink) Old 09-19-2016, 11:07 PM
Senior Member
 
Join Date: Apr 2013
Location: Canada
Posts: 271
 
My next question is what are you doing about PCV if you have a 350 and early 327 valve covers with no provision for PCV?
Darth is offline  
post #7 of 8 (permalink) Old 09-21-2016, 08:51 AM
 
 
Join Date: Oct 2012
Location: Indiana
Posts: 25
 
I used a 3/8s aluminum spacer under my stock valve covers. I'm running roller rockers and they wouldn't clear. I found these on E bay. You can't even tell they are there.
Axsom is offline  
post #8 of 8 (permalink) Old 09-25-2016, 02:55 PM
Senior Member
 
Join Date: Jul 2010
Location: Suffolk, VA
Posts: 143
 
Quote:
Originally Posted by rbwinston View Post
It seems like a new mystery every day! Keep in mind I recently bought this car (62 SS) and I didn't build the motor. Had some engine noise that was a concern, stopped by a local shop to get an opinion. Mechanic says he thinks there is one or more rockers hitting he valve cover!! So I take off the valve cover on the noisy side and sure enough there are three definite marks where the rockers were hitting, enough to cause a very small dent!! Discover what I have are 58-64 327 style valve covers on a '69 350. Apparently the 327 style covers have a tapered profile, getting slightly narrower at the top as opposed to straight sides! Obvious solution is to change covers, but my question is what is actually the difference in the heads or rockers that the 65 and up motors require a wider or "non" tapering cover?? Just curious if anyone has run into this before or you can explain what is different about either the rockers or heads. Thanks! Bob

Yes, I have experienced this problem.
1.) The valve cover can be installed 'backwards'. The inboard side of the valve cover is slightly more perpendicular than the outboard side and if they are installed backwards some (if not all) of the push rod side of the rocker arms will contact the side of the valve cover. This in not an uncommon mistake. Take it from someone who did this once upon a time.
2.) If the rocker are studs have been replace with screw-in studs (especially with guide plates) it is possible that when the holes were drilled and tapped for the studs they were drilled slightly off perpendicular. There is not a lot of clearance between the push-rod side of the valve cover and the rocker are to begin with. If the holes for the screw-in studs were drilled ever so slightly off the rocker arms can come into contact with the valve covers. (another 'first-hand' experience not easily remedied)
bowtyebob is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Impala Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome